The present invention pertains to conductive polymers and, more particularly, to conductive polymers prepared by polymerizing bisorthodinitrile monomers having diether linking groups.
Various polymers, particularly epoxides and thermoplastics, are becoming very useful in industry as substitutes for metals when reinforced by strong fibers and molded into structural materials. These materials have superior mechanical properties and are lighter and more economical to produce and transport. They, however, lack the thermal stability to operate at high temperatures and tend to oxidize and become brittle over time. They also lack the conductive characteristics of most metals they are intended to replace.
The polycyananines, epoxides, thermoplastics, and various other polymers can be made conductive, to a limited extent, by loading with metals or other conductive materials. Attempts to increase the conductivity of these reinforced polymers has mostly been limited to the uniform dispersion of fillers throughout the polymeric matrix. Most of the currently marketed conductive materials are based on the incorporation of materials such as graphite, metals, metallized glass, and carbon black into a polymeric matrix. This technique, however, has the disadvantage of increasing the cost of production since the process is more complicated and the materials are more expensive. Additionally, the greater weight due to the added filler limits the polymer use where very light weight materials are needed and adds to transportation costs.
Although intensive research efforts are being pursued to synthesize and develop conductive polymers which are intrinsically conductive, attempts to produce conductive organic polymers in the absence of dopants have had limited success. Tuemmler, U.S. Pat. No. 3,245,965, discloses a phthalocyanine which becomes semiconductive when heated. Perez-Albuerne, U.S. Pat. No. 3,629,158, discloses a composition having a polymeric anion and a fused polyacrylic aromatic hydrocarbon cation which increases in conductivity when heated. Katon, U.S. Pat. No. 3,267,115, discloses a conductive polymeric composition produced by reacting tetracyanoethylene with a metal salt.
Recently, a new class of polymers has been synthesized using bridged diphthalonitriles. These polymers have the thermal stability and structural properties necessary to replace metals in high temperature-oxidative environments but, unfortunately, lack the conductive properties of the metals they replace. Keller, U.S. Pat. No. 4,351,776, discloses a halogen-alkyl bisorthodinitrile useful in synthesizing phthalocyanines and polyphthalocyanines having high thermal stability. Keller, U.S. Pat. No. 4,315,093, discloses fluorinated polyphthalocyanines that have good thermal stability but are nonconductive. Keller, U.S. Pat. No. 4,259,471, discloses a polyphenylether-bridged polyphthalocyanine with exceptional thermal stability. In particular, Keller, U.S. Pat. No. 4,304,896, discloses the diether-linked polyphthalocyanine composition used to produce the conductive polymers of the present invention. Several polymers with delocalized pi-electron structures such as polyacetylene, poly(p-phenylene), poly(p-phenylene sulfide), and polypyrrole, have been shown to exhibit conductivity by the addition of either electron donor or electron acceptor dopants. However, a number of problems such as the inability to fabricate into films, fibers, or plastic components, conductive instability in air and boiling water, poor mechanical properties, and loss of dopant with a rise in temperature have limited their usefulness.
In recent years there has been an increasing interest in the development and utilization of intrinsically conductive organic polymers. The ideal electrically conductive polymer should exhibit good electronic conductivity, be oxidatively stable, have good mechanical properties and be normally processable. No conductive polymer with this combination of desirable properties has been reported.
Thus, synthetic polymers having the strength and thermal stability necessary to replace metals in many situations are available. There is, however, a need for a non-doped, conductive polymer having the strength and thermal stability to replace metals in situations where the material used must be conductive.